/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.context.support;

import java.util.HashSet;
import java.util.Set;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.web.context.WebApplicationContext;

/**
 * HttpServletRequest decorator that makes all Spring beans in a
 * given WebApplicationContext accessible as request attributes,
 * through lazy checking once an attribute gets accessed.
 *
 * @author Juergen Hoeller
 * @since 2.5
 */
public class ContextExposingHttpServletRequest extends HttpServletRequestWrapper {

    private final WebApplicationContext webApplicationContext;

    @Nullable
    private final Set<String> exposedContextBeanNames;

    @Nullable
    private Set<String> explicitAttributes;


    /**
     * Create a new ContextExposingHttpServletRequest for the given request.
     *
     * @param originalRequest the original HttpServletRequest
     * @param context         the WebApplicationContext that this request runs in
     */
    public ContextExposingHttpServletRequest(HttpServletRequest originalRequest, WebApplicationContext context) {
        this(originalRequest, context, null);
    }

    /**
     * Create a new ContextExposingHttpServletRequest for the given request.
     *
     * @param originalRequest         the original HttpServletRequest
     * @param context                 the WebApplicationContext that this request runs in
     * @param exposedContextBeanNames the names of beans in the context which
     *                                are supposed to be exposed (if this is non-null, only the beans in this
     *                                Set are eligible for exposure as attributes)
     */
    public ContextExposingHttpServletRequest(HttpServletRequest originalRequest, WebApplicationContext context,
                                             @Nullable Set<String> exposedContextBeanNames) {

        super(originalRequest);
        Assert.notNull(context, "WebApplicationContext must not be null");
        this.webApplicationContext = context;
        this.exposedContextBeanNames = exposedContextBeanNames;
    }


    /**
     * Return the WebApplicationContext that this request runs in.
     */
    public final WebApplicationContext getWebApplicationContext() {
        return this.webApplicationContext;
    }


    @Override
    @Nullable
    public Object getAttribute(String name) {
        if ((this.explicitAttributes == null || !this.explicitAttributes.contains(name)) &&
                (this.exposedContextBeanNames == null || this.exposedContextBeanNames.contains(name)) &&
                this.webApplicationContext.containsBean(name)) {
            return this.webApplicationContext.getBean(name);
        } else {
            return super.getAttribute(name);
        }
    }

    @Override
    public void setAttribute(String name, Object value) {
        super.setAttribute(name, value);
        if (this.explicitAttributes == null) {
            this.explicitAttributes = new HashSet<>(8);
        }
        this.explicitAttributes.add(name);
    }

}
